Steel



of an explosion followed by a violent agitaticul'ar from that already known with the- Patented Mar. 27, 1923.

CHARLESCUMINGS, or CHICAGO, ILLINOIS.

No Drawing.

To all whom it may concern:

Be it known that I, CHARLES CUMINGS, a subject of'the King of Great Britain, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvementsin Steel, of which the following is a" specification.

The invention relates to steel and has as an object the provision of a form of steel which has much improved physical properties and capabilities of working as compared with the steel at present known.

The steel provided by the present invention may be produced by the process disclosed in my application Serial Number 347,004, filed December 23, 1919. Briefly stated the process there described comprises the treatment'of the steel in its molten condition by subjecting the same to the effects tion, and preferably accompanied by a sub stantial rise in temperature.

The physical appearance of the improved steel does not differ in any substantial parpossible exception that the fractures when the metal is broken in a testing machine usually have a more perfect cup and cona form, andthe crystallin structure upon the end of the fracture is usually more of a silky nature and of finer appearance than the forms ofsteel heretofore known when not containing alloys ofraremetals.

In the cast condition the tensile strength of the improved steel increases with each .10% of carbon by from 8,000 pounds per squarelinch upwards, as compared with an "average increase of 6,000 pounds in carbon steel as heretofore manufactured. By carbon steel I intend to indicatea steel containing only very small percentages, if any, of the metals commonly alloyed with steel to improve its physical properties, such as tungsten, chromium, nickel etcj As heretofore produced byjthe best known commercial methods carbon steel in its condition as cast and normalized has had an average tensile strength with 20% carbon of about 52,400 pounds per square inch and with 50% carbon of about 71,000 pounds per square inch. The improved steel of the present invention under like treatment with the exception of the process described in my copendiug application above referred to, and

spheres. substantial freedom from slag is intended to Application filed December 10, 1921 Serial No. 521,476.

with substantially the same chemical analysis shows for 20% C. a tensile strength of approximately 7 0,000 pounds per square inch and for .50% C. a tensile strength of applroximately 100,000 pounds per square inch. ot' only has the improved steel a high tensilestrength as compared with steel heretofore known but its elastic limit is higher in proportion to its tensile strength being approximately 80% thereof. The elastic limit of carbon steels heretofore known has been about 70% of its tensile stren h. The Brinnell hardness of the improve steel is also greater than the steel of the rior art of like chemical composition. Car on steel as heretofore known increases in tensile strength under heat treatment and forging tofore -made contained its slag inclusions in various irregular forms elongated in all directions, which forms have a very much more deleterious effect upon the strength of the steel than do inclusions in the form of The reference in the claims to a refer tothe comparative freedom as compared with steel heretofore known and not to an actual absence of any slag inclusions.

It is found that the improved steel yields more readily to heat treatment than steel of like chemical composition heretofore known. That is to say, the time required for the point of decalescence while the temperatureof the steel is being raised is much shorter than former steels of like chemical composition. After the steel is normalized it may be raised to a much higher temperature without injury than has been the case with former steels and the resulting wider range of temperatures which may be applied in heat treatment results in a reduced liability of injury.

lVhen the improved steel is poured from the furnace into the ladle or mould it pours much more quietly and is found to flow more readily in casting than steel heretofore known. As the result of this quality very thin sections may be cast Without liability to blow-holes or cavities.

It is found that the readiness with which the steel forges is much improved, and that during machining operations it cuts more smoothly, leaving edges which have not the torn appearance which sometimes appears with steel now in use. The improved action on forging and shaping by cutting is believed to be due to the more homogeneous structure and to the finer grain of the steel which qualities are plainly exhibited by photomicrographs of etched samples. In the normalized state the pearlite shown by such samples shows a structureapproaching the sorbitic rather than lamellar, as is usual in steels under like conditions. Normalize as used herein and in the claims is intended to refer to heating the steel to a temperature above the point of decalescence and slowly cooling.

Minor changes may be made in the steel from the physical properties claimed in the following claims without departing from the spirit of the invention.

I claim:

1. A carbon steel the elastic limit of which is at least 80% of its tensile stren h.

2. A carbon steel which after eing normalized and subsequently heated to a temperature above its point of decalescence and quenched has its tensile strength increased at least 100% by the heat treatment.

3. A carbon steel which after being normalized and subsequently heated to a temperature above its point of decalescence and quenched has its tensile strength increased at least 75% by the heat treatment.

4. A carbon steel having not more than .50% carbon, which when cast and normalized, has a tensile strength of at least 90,000 pounds per square inch.

5. A carbon steel having not more than 50% carbon, which when cast and normalized has a tensile strength of at least 100,000 1 pounds per square inch.

6. A series of carbon steels of varying proportions of carbon, the individuals of said series having a tensilestrength which varies by at least 8,000 lbs. per square inch with each difference of 10% of carbon.

7. A carbon steel made by the process herein referred to which in normalized condition has its tensile strength increased at least 8,000 pounds per square inch by an addition of 10% of carbon.

8. A carbon steel made by the process herein referred to which in normalized condition has its tensile strength increased at least 10,000 pounds per square inch by an addition of .10% of carbon.

CHARLES CUM-INGS. 

